Fix typos

Author: odersky

docs/docs/reference/derivation.md

@@ -57,10 +57,10 @@ This is all a user of typeclass derivation has to know. The rest of this page co
 
 For every class with a `derives` clause, the compiler computes the shape of that class as a type. For instance, here is the shape type for the `Tree[T]` enum:
 ```scala
-Cases[
+Cases[(
   Case[Branch[T], (Tree[T], Tree[T])],
   Case[Leaf[T], T *: Unit]
-]
+)]
 ```
 Informally, this states that
 
@@ -88,10 +88,10 @@ Case[Labelled[T], (T, String)]
 ```
 And here is the one for `Option[T]`:
 ```scala
-Cases[
+Cases[(
   Case[Some[T], T *: Unit],
   Case[None.type, Unit]
-]
+)]
 ```
 Note that an empty element tuple is represented as type `Unit`. A single-element tuple
 is represented as `T *: Unit` since there is no direct syntax for such tuples: `(T)` is just `T` in parentheses, not a tuple.
@@ -225,7 +225,7 @@ trait Eq[T] {
 We need to implement a method `Eq.derived` that produces an instance of `Eq[T]` provided
 there exists evidence of type `Generic[T]`. Here's a possible solution:
 ```scala
-  inline def derived[T, S <: Shape](implicit ev: Generic[T]): Eq[T] = new Eq[T] {
+  inline def derived[T](implicit ev: Generic[T]): Eq[T] = new Eq[T] {
     def eql(x: T, y: T): Boolean = {
       val mx = ev.reflect(x)                    // (1)
       val my = ev.reflect(y)                    // (2)
@@ -322,9 +322,9 @@ calling the `error` method defined in `scala.compiletime`.
 **Example:** Here is a slightly polished and compacted version of the code that's generated by inline expansion for the derived `Eq` instance of class `Tree`.
 
 ```scala
-implicit def derived$Eq[T](implicit elemEq: Eq[T]): Eq[T] = new Eq[Tree[T]] {
+implicit def derived$Eq[T](implicit elemEq: Eq[T]): Eq[Tree[T]] = new Eq[Tree[T]] {
   def eql(x: Tree[T], y: Tree[T]): Boolean = {
-    val ev = implOf[Generic[Tree[T]]]
+    val ev = implicitly[Generic[Tree[T]]]
     val mx = ev.reflect(x)
     val my = ev.reflect(y)
     mx.ordinal == my.ordinal && {